Majority of them are just scams. There's no way on earth that you would mine anything worthwhile from a mobile phone. Back in the day when we could CPU mine, sure, you might have earned something. However, today it's all about ASICs (Application Specific Integrated Circuits) - machines that are designed to mine bitcoin. The only issue is, to mine anything decent, they use a LOT of power. And they being, you need more than one. And it's the electricity cost to run them that is the killer.
i remember when mining was something you could do casually maybe with laptop or desktop but now? it's like the game's changed completely. it's all about having industrial scale equipment and basically using up a small power plant's worth of electricity. It feels like the only people who can win are the big players who already have the resources